Infrared charge transfer device (CTD) system

Abstract

An infrared charge transfer device (CTD) imaging system is disclosed which includes an optic system for focusing infrared energy emanating from a scene, a detector matrix for receiving the focused infrared energy and converting it to electrical signals representative of the intensity of the infrared energy, and a video processor for processing the electrical signals into video signals. The detector matrix of the system is a plurality of IR detector cells arranged in rows and columns. Each detector cell includes a substrate of semiconductor material, an integrating electrode, a drain electrode, a transfer electrode and insulating layers. The integrating electrode is centrally disposed with respect to the drain and transfer electrodes with the integrating electrode in a spaced relationship with the drain electrode. The integrating and drain electrodes form first level MIS electrodes on the semiconductor substrate. The transfer gate forms a second level MIS electrode as to the semiconductor substrate and overlaps the space between the integrating and drain electrodes. In a second MIS embodiment the drain electrode is replaced by a diode formed in the semiconductor substrate. In both embodiments, the integrating electrodes are connected together in columns and the transfer electrodes are connected together in rows. In operation, the integrating electrode and the drain are on while a row of transfer electrodes are turned on and then off transferring the charge from wells under the integrating electrode to the drain well. The column voltages are sampled before and after the turn-on and turn-off of the integrating well the voltage difference on the column lines is proportional to the charge transferred and is used to indicate the intensity of the impinging infrared image. Charge collected by the drain is either injected to the substrate in the first embodiment or drained out the contact to the junction diode in the second embodiment.

What is claimed is: 
     
       1. An infrared imaging system including an optical means for focusing infrared energy emanating from a scene comprising: (a) an MIS detector matrix for receiving the focused infrared energy in the field-of-view of the optical means and converting such energy into electrical signals representative of the impinging infrared energy, said detector matrix including a plurality of detecting cells formed on the infrared sensing semiconductor material, each cell having an integrate well formed by an MIS electrode for collecting charges generated by the impinging infrared energy, a transfer MIS gate for selectively transferring the charge from the integrate well, and drain means common to selected cells to drain the charge out of the integrate wells responsive to said transfer gate; and   (b) means connected to the integrate wells for measuring voltage difference of the integrate wells with and without the charges and processing video signals representative of the voltage differences.   
     
     
       2. An infrared imaging system according to claim 1 wherein each of said cells includes an integrate MIS electrode on the slab of infrared sensing semiconductor material, said electrode having portions transparent to infrared energy for forming preselected light sensitive areas in said slab of semiconductor material and opaque conductor portions electrically connected to the transparent portions of said electrodes. 
     
     
       3. An infrared imaging system according to claim 2 wherein each said cell further includes a via electrically connecting the opaque portions of the transparent integrate MIS electrode to a column line. 
     
     
       4. An infrared imaging system according to claim 3 wherein the vias contain metal which is of a thickness sufficient to ensure continuity through the via. 
     
     
       5. An infrared imaging system according to claim 4 wherein the metal contained in the via is indium. 
     
     
       6. An infrared imaging system according to claim 1 wherein said transfer gate electrodes are connected in rows. 
     
     
       7. An infrared imaging system according to claim 1 wherein the common drain means surrounds each integrate MIS electrode of the plurality of cells in a spaced relationship thereto. 
     
     
       8. An infrared imaging system according to claim 6 wherein the common drain means and integrate MIS electrode are formed from a first level MIS metalization on the slab of semiconductor material. 
     
     
       9. An infrared imaging system according to claim 8 wherein the common drain is connected to a biasing circuit which periodically collapses the MIS potential well of the drain and injects the charge in the drain well into the substrate. 
     
     
       10. An infrared imaging system according to claim 6 wherein said transfer gate covers in a spaced relationship the space between the integrate electrode and the common drain means thereby forming a second level MIS electrode on the slab of semiconductor material. 
     
     
       11. An infrared imaging system according to claim 1 wherein the common drain means comprises a junction diode. 
     
     
       12. An infrared imaging system according to claim 11 wheren the junction diode common drain is connected to a biasing circuit which removes from the drain the charge transferred from the integrate wells.